An outboard motor question for the experts.

gitrdun · #1 06-24-2016, 03:59 PM

My outboard is a vintage 1970's Johnson 55hp Sea Horse, 2 stroke. It is mint, has low hours, very tight, runs great. My gas tank has about 2 or so gallons of pre-mixed gas in it. I think (not sure) that I put fuel stabilizer in it, but I did not use it at all last summer. I serviced it, changed the oil in the leg, and fired it up and it seems to run great, on dry land with the rabbit ears. I wonder if this engine would benefit from using premium vs regular gas. And if I should get rid of the old gas, how does one properly dispose of it?

Bemoredog · #2 06-24-2016, 06:11 PM

Don't use premium unless the engine manufacturer specifies it. Premium is a misnomer. It doesn't mean "better gasoline". Certain engines actually require certain octanes because of their combustion timing. If you put premium in an engine not designed for it, chances are you could hurt it. Most modern engines can account for different octanes of gasoline to avoid pinging, but you gain ZERO ADVANTAGE to using the premium gas. It won't run better, it won't run more powerfully. Use the spec that the engine was designed for. Please trust me on this. I've done pretty serious research on the topic. As well, a simple Google search will turn up the same answers.

As far as using the old gas: that's up to you. If the engine runs fine with rabbit ears there's a good chance you're fine. Modern gasoline is very tolerant to degradation. You could also remove half the old gas and mix in a half measure of new gas if you want to compromise. If you remove all the old gas bring it to me, I'll take it off your hands

You can likely dispose of it at a Canadian Tire store. I take my old oil and fluids there.

Personally I'd just use the gas.

Big Bull · #3 06-24-2016, 07:37 PM

I would respectably disagree with Bemoredog. I would not run old fuel through the motor and I would only buy ethanol free fuel, i.e. Shell V-Power premium. If you are using the motor continuously, you would be fine with fuel that contains ethanol. If the motor doesn't get a lot of use, ethanol can cause problems in your carb, gaskets, and rubber components. Finding ethanol free fuel can be hard to find, depending on your location. Check out iBoats forum for more info.

Moosetalker · #4 06-24-2016, 10:50 PM

I agree with BB Premium gas for sure make sure its ethanol free. Most big retailers will have the Premium blend 0% ethanol tag on the pump Costco and Shell Do as well as some Esso's. if its not there don't trust it ethanol blended fuel's DE-stabilize after 30 days.
Octane levels on the old leaded gasoline were slightly higher than today's. Seafoam added to tank will make it last longer and has extra lubricants to make up for no lead in the new fuel's.

And as an aside make sure your tank is cleaned out with carb cleaner if its been sitting long the Varnish from fuels breaking down can become dislodged and gum up your carb.

Kim473 · #5 06-25-2016, 04:32 AM

Poor the 2 gallons of fuel into your truck with a full tank of gas.

calgarygringo · #6 06-25-2016, 07:35 AM

I have the same scenario. 2x70's vintage hardly used Evinrude 50 and 15 hp. I run Shell premium in them for reasons mentioned. Any leftover gas I dump into my truck in the fall and start fresh in the spring. Run a bit of Seafoam through too at the beginning of the year and your older motor will run as good as new.

Walleyedude · #7 06-25-2016, 10:04 AM

Another vote for premium ethanol free fuel ONLY. I've experienced first hand the problems ethanol can cause and I avoid it like the plague.

In addition, as others have said, the added octane is closer to the leaded gasoline your motor was designed to run on. It definitely won't hurt it in any way.

Poor the old gas into your vehicle when you're close to empty and then top it up with new fuel and you'll be totally fine.

skidderman · #8 06-25-2016, 10:59 AM

Quote:

Originally Posted by Big Bull

I would respectably disagree with Bemoredog. I would not run old fuel through the motor and I would only buy ethanol free fuel, i.e. Shell V-Power premium. If you are using the motor continuously, you would be fine with fuel that contains ethanol. If the motor doesn't get a lot of use, ethanol can cause problems in your carb, gaskets, and rubber components. Finding ethanol free fuel can be hard to find, depending on your location. Check out iBoats forum for more info.

This!!!!!!!

Big Bull · #9 06-25-2016, 02:45 PM

Quote:

Originally Posted by Jet

I disagree with everyone :-)

2. Use ethanol free at the octane rating recommended I.E. If regular is recommended and is the only one the engine supports, then find ethanol free regular.

Didn't even know it was an option. Closest ethanol free fuel to me is 75 km away, so that's why I go with the V-Power.

skidderman · #10 06-25-2016, 03:06 PM

No such thin as far as I know. Even some premium has ethanol. I've worked on lots of engines that were in trouble because of ethanol. I've witnessed a carb where nothing could fix it but a new carb. Ethanol sucks!!!!

Walleyedude · #11 06-25-2016, 03:41 PM

Your old outboard has zero electronic controls to adjust timing and likely runs at a fairly conservative compression ratio, so there's no performance gains to be had from premium.

There's no negatives to running premium in terms of performance, it won't harm your engine in any way.

The only downside to premium is price. The upside of being ethanol free is worth every penny in my opinion.

As a side note for people out there running Mercury Verados, especially the L6's, there is a substantial performance increase when running premium fuel.

gitrdun · #12 06-25-2016, 06:58 PM

Thanks for the replies guys. Based upon what I've learned here, I will run no ethanol premium. I've also picked up some SeaFoam at CT. As far as the old gas is concerned, I'll put it in another container and decide later as I can't run it in my truck, it's diesel.